Recently, glass bottles have been gradually replaced by PET bottles, particularly for the sale of soft drinks, for the following reasons. The sale of soft drinks offers the manufacturer the advantage of higher volumes per unit sold. Furthermore, the consumer is offered the convenience of higher volumes of product per unit weight.
Where the infrastructure exists to apply the process of returning, cleaning and reusing PET-bottles, there is the additional possibility of cost saving.
Systems for glass bottle washing are mature and with the gradual replacement of glass by PET, the tendency has been to clean PET bottles by the same process. Although current systems achieve effective results, the process is far from optimal.
Generally, the cleaning of the bottles occurs immediately before refilling, thus minimizing the risk of resoiling and infection. Cleaning is effectively carried out in an industrial bottle washer which typically can handle from 5000 to 100,000 bottles per hour, depending on the machine capacity.
The conventional cleaning solution usually contains about 1% by weight of sodium hydroxide and an antifoam agent and is applied at a temperature of about 60.degree. C. It is often applied by way of a soaking stage followed by a spray stage, prior to rinsing, or else by just spraying before rinsing.
Since the bottle cleaning process occurs immediately before filling of the bottles in a continuous feed process, this cleaning process could be considered to constitute an intrinsic part of the bottling process.
The conventional bottle cleaning process usually takes about 25 minutes per bottle. It would be commercially highly attractive if this cleaning time could be reduced while retaining good cleaning performance.
It is therefore an object of the present invention to provide a method of cleaning returnable bottles, particularly PET bottles, which takes less time than the known methods of the prior art but gives substantially equal cleaning performance.